This invention relates to steam turbine plants and more particularly to systems for regulating the flow of steam to turbines.
It is known that the supply of steam to a turbine in a steam turbine plant may be regulated by installing a pressure measuring instrument on the upstream side of the turbine intake valve. In the event of a rapid reduction in the power required from the turbine, for example in the case of a short circuit or stroke of lightening in one section of the power network, the turbine intake valves close and bypass valves open rapidly. As a result, considerable changes in steam pressure will occur upstream from the valves. These changes in steam pressure will advance along the line at substantially identical velocities in the direction of the source of the steam. Especially large pressure variations are found immediately in front of the turbine intake valve, which is where the pressure measuring instrument is typically located. When the steam is being generated by a nuclear power plant this arrangement will adversely influence the parameters established by the reactor manufacturer for the initial pressure control to such an extent that limits of the value: ##EQU1## might be exceeded. In this formula, Q.sub.VE represents the flow through the turbine intake valve, Q.sub.BP represents the flow through the bypass valve and Q.sub.RE represents the flow from the reactor outlet aperture. These limiting values are not exceeded if the changes in opening and closing of the valves occurs relatively slowly. Very rapid changes in the position of the valves, which is desirable under ordinary circumstances, could not be utilized heretofore within the specific limits set for operation of nuclear power plants.
It is an object of this invention to provide a steam power plant in which these disadvantages are overcome, specifically wherein the turbine inlet and bypass valve are capable of changing position rapidly while still maintaining the limits established by the manufacturer of the reactor.